Notes on Family: Geminiviridae

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This family is characterised by its twinned (geminate) icosahedral particles and a circular, single-stranded DNA genome in one or two components. The only other known plant viruses with ssDNA genomes have many more, smaller, segments and are placed in the family Nanoviridae. Genera are distinguished by the number of genome segments, genome organization, the type of vector and the host plants infected.

Mono-, or bi-partite, circular single-stranded DNA. Total genome 2500-3000 or 4800-5600 nucleotides. There are coding regions in both the virion (+) and complementary (-) sense strands. All members have a single coat protein of 28-34 kDa and a replication (Rep) protein of c. 41 kDa, that initiates rolling-circle replication. In all members, there is a potential stem-loop structure in the intergenic region that includes a conserved nonanucleotide sequence (TAATATTAC; TAAGATTCC in some genera) where ssDNA synthesis is initiated.